Effects of environmental enrichment and paradoxical sleep deprivation on open-field behavior of amphetamine-treated mice

Background: Environmental enrichment or paradoxical sleep deprivation (PSD) has been shown to modify some responses elicited by drugs of abuse. The aims of the present study were to examine the effects of environmental enrichment and PSD, conducted separately or in association, on open-field behavior elicited by amphetamine (AMP) in mice. Methods: Male C57BL/6 mice were randomly assigned to live in either an enriched environmental condition (EC) or a standard environmental condition (SC) for 12 months since weaning. Some of the EC and SC mice were sleep deprived for 48 h, while others were maintained in their home-cages. Immediately after PSD or home-cage stay, the animals received an ip injection of saline, 2.5 mg/kg AMP or 5.0 mg/kg AMP. Fifteen minutes later, their open-field behavior was quantified. Results: Whereas PSD enhanced total and peripheral locomotor activity of acutely AMP-treated mice, environmental enrichment presented only a trend toward enhancement. When PSD and environmental enrichment were combined, an increase in the total and peripheral locomotion frequencies of AMP-treated animals, similar to that observed after PSD, was revealed. In addition, PSD, environmental enrichment or their combination did not modify the effects of AMP on the other open-field behavioral parameters that were analyzed. Conclusion: The present findings demonstrate that some (but not all) of the behavioral effects caused by AMP acute administration can be similarly and specifically enhanced by both environmental enrichment and PSD in C57BL/6 mice. (C) 2007 Elsevier Inc. All rights reserved.